Separating disks for centrifuges



Aug. 15, 1967 .1. PUTTERLl K 3,335,946

SEPARATING DISKS FOR CENTRIFUGES Filed April 12, 1965 INVENTOR.

United States Patent VO 3,335,946 SEPARATING DISKS FOR CENTRIFUGES JanPutterlik, Prague, Czechoslovakia, assignor to Ceskoslovenska akademieved, Prague, Czechoslovakia Filed Apr. 12, 1965, Ser. No. 447,209 Claimspriority, application Czechoslovakia,

Apr. 14, 1964, 2,155/64 2 Claims. (Cl. 233-41) This invention relatesgenerally to the separating disks of centrifuges used in separating theliquid and solid constituents of a slurry or dispersion so as to obtaina concentrated slurry or dispersion, that is, the solids with a muchreduced proportion of the liquid, or a clarified liquid.

Centrifuges of the type described above generally include a hollow bowlrotated about its axis and containing an axial series of spaced,frusto-conically shaped separating disks of somewhat smaller diameterthan the bowl shell. The slurry, dispersion or other incoming materialto be centrifuged, is admitted through feed channels which dischargenear the outer edges of the separating disks, and the clarified liquidis removed from the bowl through an outlet positioned at or near theaxis of rotation. Thus, the liquid constituent is made to flowcentripetally, or radially inward, through the spaces between theseparating disks in order to reach the outlet for the liquid and, duringsuch flow, the solid particles are driven centrifugally so as to collectin the radially outward portion of the bowl shell beyond the perimetersof the separating disks. Discharge nozzles are further provided, incertain existing centrifuges, for discharging the concentrated solidswhich collect in the outer peripheral portion of the bowl shell.

In existing centrifuges of the described character, the separating disksare formed of thin sheet metal which is either stainless steel ortreated so as to resist corrosion. Such existing sheet metal separatingdisks are further provided with spacing projections in the form of metalstampings which are welded to the conical surfaces of the disks atradially spaced intervals. It will be apparent that the manufacture ofsuch sheet metal separating disks is difiicult and costly, as the disksmust be accurately shaped and have smooth surfaces in order to ensurethe high operating efliciency, and relatively low power consumption ofthe centrifuge.

The existing separating disks of sheet metal have two furthersubstantial disadvantages. The sheet metal pre viously used for theseparating disks has a high modulus of elasticity in tension, forexample, up to 20,000 kg./mm. in the case of steel, and, by reason ofsuch high modulus of elasticity, the separating disks formed of sheetmetal respond readily to vibration of the bowl or rotor of thecentrifuge, which vibration may result from the dynamic unbalance of theseparating disks. The vibrations of the separating discs interfere withthe centrifugal separation of the dispersion or slurry in the thinlayers or flows passing between the separating disks. Further, the sheetmetal for forming the separating disks usually has a specific gravity ofapproximately 8.0 which may be almost eight times larger than thespecific gravity of the dispersion flowing between the separating disksso that any inaccuracy in the shape and balance of the separating diskswith respect to the axis of rotation constitutes a source of dynamicunbalance giving rise to vibration of the rotated bowl or rotor. Suchdynamic unbalance cannot be easily eliminated by balancing of theseveral separating disks, as it is difiicult to ensure the samerelatively large number of disks will be assembled in the same order orsequence whenever the bowl or rotor is opened and has the disks removedtherefrom.

Accordingly, it is an object of this invention to provide separatingdisks for centrifuges which avoid the above mentioned disadvantages ofthe separating disks that have been heretofore available.

In accordance with an important aspect of this invention, separatingdisks for centrifuges are formed of a material having a modulus ofelasticity which is no greater than 1,000 kg./mm. and a specific gravityno greater than approximately 2.0, that is, not exceeding approximatelytwo times that specific gravity of the dispersion which is to becentrifuged.

The above, and other objects, features and advantages of this invention,will be apparent in the following detailed description of anillustrative embodiment thereof which is to be read in connection withthe accompanying drawing, wherein:

FIG: 1 is an elevational view of a separating disk for a centrifuge inaccordance with this invention; and

FIG. 2 is a sectional view taken along the lines 22 on FIG. 1.

Referring to the drawing in detail, it will be seen that a separatingdisk 10 embodying this invention may be generally fr-usto-conical inshape and have radially directed rims 11 and 12 extending along itsinner and outer peripheries. At least one of the conical surfaces of thedisk 10 has suitably spaced projections 13 extending therefrom for thepurpose of uniformly spacing apart adjacent separating disks when thelatter are assembled in the bowl or rotor of a centrifuge.

In accordance with this invention, the separating disk 10 is formed of amaterial having a modulus of elasticity not greater than approximately1,000 kg./mm. and a specific gravity not greater than approximately 2.0.Many different types of synthetic resin materials satisfy the foregoingrequirements for forming separating disks in accordance with thisinvention, such as, for example, polyethylene, polyvinyl chloride,polypropylene, textile and glass laminates, resins and the like.Separating disks for centrifuges formed of such synthetic materials inaccordance with this invention can be conveniently molded, for example,by injecting molding, so that the spacing projections 13 can besimultaneously formed with the remainder of each separating disk andform integral parts of the latter.

When separating disks are formed of a material with a relatively lowmodulus of elasticity, as in accordance with this invention, such disksserve to damp the vibrations of the rotated rotor or bowl and thus donot vibrate or respond to vibration of the rotor or bowl arising fromany dynamic unbalance of the latter. By reason of their vibrationdamping properties, the separating disks embodying this invention securethe smooth and elfective centrifugal separation of the solids from theliquid constituents in the layers of flows passing between the adjacentseparating disks. Due to the fact that the material forming theseparating disks in accordance with this invention has a specificgravity which is much closer to the specific gravity of the dispersionor slurry being centrifuged than is the specific gravity of thepreviously known sheet metal separating disks, the disks embodying thisinvention do not cause any appreciable or significant dynamic unbalanceof the rotor or bowl. Even if there are inaccuracies in the shapes ofthe separating disks embodying this invention or in their concentricitywith respect to the axis of rotation, such inaccuracies aresubstantially compensated by the filling of the spaces between adjacentseparating disks with the dispersion flowing therethrough and having aspecific gravity which is, at the worst, only one-half of the specificgravity of the material forming the disks.

Since separating disks embodying this invention can 3 be convenientlymolded by injection molding or other conventional molding procedures,the same can be very economically produced, particularly when oneconsiders that the spacing projections are simultaneously formedthereon, rather than being separately attached, as in the case of thepreviously existing sheet metal separating disks, It will also beapparent that injection molded separating disks embodying this inventioncan be formed with a perfectly accurate shape and with smooth surfacesso as to promote the effective centrifugal separation of the liquid andsolid constituents of a dispersion.

Although the materials proposed for forming of the separating disks inaccordance with this invention have a strength which is relatively lowwhen compared with that of the sheet metal previously used forseparating disks, such relatively low strength is not disadvantageous byreason of low specific gravity of the proposed materials which makes itpossible for the stress resulting from the centrifugal force to becompensated, at least to a considerable extent, by the centripetal, orradially inwardly directed force or hydrostatic lift acting on theseparating disks as a result of the radially inwardly directed flowbetween adjacent disks. The separating disks formed from the proposedsynthetic materials in accordance with this invention have a furtheradvantage in the resistance to abrasion of such materials by thedispersion flowing between the separating disks.

Although an illustrative embodiment of this invention has been describedin detail herein with reference to the accompanying drawing, it is to beunderstood that the invention is not limited to that precise embodiment,and that various changes and modifications may be effected therein byone skilled in the art without departing from the scope or spirit of theinvention, except as defined in the appended claims.

What is claimed is:

1. A separating disk for a centrifuge, said disk being of a materialhaving a specific gravity of less than approximately 2.() and a modulusof elasticity in tension of less than approximately 1000 kg./mm.

2. A molded separating disk for a centrifuge, said disk being ofgenerally frusto-conical configuration and having integral spacingprojections extending from at least one surface thereof, said disk beingof a synthetic material having a specific gravity of less thanapproximately 2.0 and a modulus of elasticity in tension of less thanapproximately 1000 kg./mm.

References Cited UNITED STATES PATENTS 989,099 4/1911 Wright 233-1,168,452 1/ 1916 Anderson 233-29 3,235,174- 2/1966 Downey 233-l9 M.CARY NELSON, Primary Examiner.

H. KLINKSIEK, Assistant Examiner.

1. A SEPARATING DISK FOR A CENTRIGUGE, SAID DISK BEING OF A MATERIALHAVING A SPECIFIC GRAVITY OF LESS THAN APPROXIMATELY 2.0 AND A MODULUSOF ELASTICITY IN TENSION OF LESS THAN APPROXIMATELY 1000 KG./MM.2.